Optical switching devices, logic elements and other computer components have been the subject of research because of the desirability of optical systems in many circumstances. Optical computer systems offer the advantages of high operating speeds, immunity to electrical noise and lower power requirements. Such systems can be entirely optical, wherein all data and control signals are in optical form without conversion to electronic signals. A general discussion of optical switching networks is given by Hinton in "Architectural Considerations for Photonic Switching Networks", IEEE Journal on Selected Areas in Communications, Vol. 6, No. 7, August 1988, pages 1209-1226.
U.S. Pat. No. 4,863,247, issued Sep. 5, 1989 to Lasher et al, discloses trinary optical logic systems using an optical three-state polarization scheme.
U.S. Pat. No. 4,811,258, issued Mar. 7, 1989 to Andersen et al, discloses an optical logic gate using nonlinear reflection and refraction at an interface.
U.S. Pat. No. 4,926,366, issued May 15, 1990 to Cuykendall et al, discloses thin film optical computing circuits including a thin film half adder, a full adder and a carry-propagate adder.
U.S. Pat. No. 4,761,060, issued Aug. 2, 1988 to Sawano, discloses an optical D-type flipflop that uses an optical switch and an optical bistable element.
U.S. Pat. No. 4,922,497, issued May 1, 1990 to Mori et al, discloses an optical logic circuit using a semiconductor laser.
U.S. Pat. No. 4,910,737, issued Mar. 20, 1990 to Payne et al, discloses a bistable optical fiber device that can be used for logic memory and regenerative amplification applications.
U.S. Pat. No. 4,900,115, issued Feb. 13, 1990 to Heuring et al, discloses optical logic circuits including a lithium niobate switch and an optical fiber loop as a delay line memory.
U.S. Pat. No. 4,875,181, issued Oct. 17, 1989 to Hagemeyer, discloses a device for performing logical operations wherein the plane of polarization of linearly polarized light is distorted by electric or magnetic fields.
U.S. Pat. No. 4,786,128, issued Nov. 22, 1988 to Birnbach, discloses a multilayer device for modulating and reflecting light, comprising an electro-optic layer with a variable index of refraction. The device can be used as an optical logic element.
U.S. Pat. No. 4,707,081, issued Nov. 17, 1987 to Mir, discloses a linear light valve array having discretely addressable electro-optic gates for selectively changing the polarization of incident polarized light.
U.S. Pat. No. 4,689,793, issued Aug. 25, 1987 to Liu et al, discloses optical logic gates and circuits based direct polarization switching in a semiconductor laser.
U.S. Pat. No. 4,632,518, issued Dec. 30, 1986 to Jensen, discloses a nonlinear optical logic device in which two input light beams having independent modes are launched. The device operates independently of the relative phases of the two inputs.
U.S. Pat. No. 4,262,992, issued Apr. 21, 1981 to Berthold III, discloses an integrated optical logic element formed on a substrate of electro-optic material, capable of being controlled to perform different logic operations.
U.S. Pat. No. 4,128,300, issued Dec. 5, 1978 to Stotts et al, discloses a generalized optical logic element capable of simultaneously performing different logic functions.
U.S. Pat. No. 3,984,785, issued Oct. 5, 1976 to Riseberg et al, discloses an optical logic device which includes a laser resonator which in turn includes means for producing an optical laser output having a direction of polarization along selectable directions.
U.S. Pat. No. 3,849,740, issued Nov. 19, 1974 to Brandt, discloses an integrated thin film logic gate including two input waveguides to a laser active film and one waveguide output from the laser active film.
U.S. Pat. No. 3,637,287, issued Jan. 25, 1972 to Hansen, discloses techniques for reducing the opening time of optical gates employing a gate medium in which birefringence is optically induced.
U.S. Pat. No. 4,363,106, issued Dec. 7, 1982 to Tai, discloses a computation module for an optical computer based on the residue number system.
U.S. Pat. No. 3,448,282, issued Jun. 3, 1969 to Fleisher et al, discloses an optical AND gate employing linearly polarized light and a tube having a photocathode.
U.S. Pat. No. 4,932,739, issued Jun. 12, 1990 to Islam, discloses optical logic devices which utilize soliron trapping between two optical signals propagating in a birefringent fiber.
U.S. Pat. No. 4,867,515, issued Sep. 19, 1989 to Normandin, discloses an optical modulator which utilizes a channel waveguide and an optical control signal.
All of the known prior art optical switching components have had serious disadvantages, including relatively slow switching speeds, high power requirements, and the like.
It is a general object of the present invention to provide novel optical switches.
It is another object of the present invention to provide apparatus for performing binary arithmetic operations using optical signals.
It is a further object of the present invention to provide optical switching components which require low power.
It is a further object of the present invention to provide optical switching components based o.sub.n controlled transmittance of light through a semi-transparent metallic film.
It is a further object of the present invention to provide optical switching components based on controlled rotation of the plane of polarization of an input optical signal by an optically active substance.